Research On The Indetification Index Of Vulnerable Components In Power Grid Based On Complex Network Theory

The vulnerability of power grid has been viewed through many times of large-scaleblackout caused by cascading failures rencently. As a significant branch of power gridvulnerability research, the vulnerability assessment based on Complex Network Theoryhas been widely studied, aiming at indetifying the vulnerable components so as to takesome effective measures to prevent blackout. The paper makes a further research to theidentification index of vulnerable components in power grid with Complex NetworkTheory, considering physical and operational characteristics of power gird to identify thevulnerable componets. Main work of this paper is dwelt on as follows:Firstly，a new method to assess vulnerable lines and nodes of power grid from thestructural perspective is proposed. Transmission contribution degree is defined to identifyvulnerable lines and nodes based on maximum flow and Complex Network Theory, itreflects the ability of lines and nodes to undertake the transmission of power flow inpower grid. The method can overcome the limitation that power flow is supposed to betransferred along the shortest path when compared with the present research, and take allpossible transmission paths among different “source-load” pair into consideration basedon the whole structure of power network. At the same time, power gird is regarded as adirected and weighted network, and power transfer ability of lines is taken into account,thus the physical background is more suitable for the actual power system. The test onIEEE-39power system demonstrates the validity when compared to the present methods.Secondly，a method of identifying the vulnerable components in a power gridconsidering the risk of impact by power flow which may lead to cascading failures isproposed. With the distribution and fluctuation of power flow due to the removal of linesand load disturbance of nodes, the index of overload entropy、the first and second kind ofindex related to power flow fluctuation, these indexs consider the whole impact by powerflow due to disturbance, and they are used to assess the vulnerable components withtransmission betweenness which reflects the structural characteristic of power grid. Thetest on IEEE-39power system demonstrates the rationality and validity of the proposal method.Thirdly, efficiency of power flow transmission is proposed to assess the functionalpeformance of power grid, and the vulnerability of components is calculated based on thefluctuation of efficiency of power flow tranmission before and after the removal ofcomponents. Efficiency of power flow transmission takes the result of tracing power flowas the foundation, to some extent，it combines the operational mode of power grid, thethought of integrative vulnerability assessment is viewed. At the same time, thevulnerability of power grid with distributed generation is studied, the research resultsshow that the quantum of local power supply increased, the efficiency of power flowtransmission ascended. The ability of defending attack with and without distributedgeneration are compared：when suffers single attack or cascading random attack, thedefensive ability rised with distributed generation. However, under intended attack, theperformace of defending during the prior period of attacking is better than that of the laterstage.Forthly， the application of vulnerable componets’ assessment is studied, theAllocation strategy of node capacity based on structural vulnerability is proposed, it can beused to guide the prevention of cascading failures.